From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7178C74A5B for ; Wed, 22 Mar 2023 22:48:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229843AbjCVWsO (ORCPT ); Wed, 22 Mar 2023 18:48:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229497AbjCVWsM (ORCPT ); Wed, 22 Mar 2023 18:48:12 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0834455B7 for ; Wed, 22 Mar 2023 15:48:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id AE612B81E2A for ; Wed, 22 Mar 2023 22:48:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 680F1C433D2; Wed, 22 Mar 2023 22:48:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1679525282; bh=BGKyyAA4QpG6Z1GWxU+oGVhXPmVwsT4Le2J+vviX+7w=; h=Date:To:From:Subject:From; b=k5IomJj9ZVlLRG4U6m2gL0MLIqlRkNsqx+3kn5kTTRgSquQdQzz7zuYUuOFPKXFjQ kawVqjS+HgpW5BEusVCsgd4JalHcQs+56p9srJr5sTBVmfA6mzunmYtcACsPlPcpWj as33fxB8GoDWQ1fLXhPUM0/aTA8iskuCTHhbdmvs= Date: Wed, 22 Mar 2023 15:48:01 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, vernon2gm@gmail.com, vbabka@suse.cz, Liam.Howlett@oracle.com, david@redhat.com, lstoakes@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-mmap-vma_merge-explicitly-assign-res-vma-extend-invariants.patch added to mm-unstable branch Message-Id: <20230322224802.680F1C433D2@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/mmap/vma_merge: explicitly assign res, vma, extend invariants has been added to the -mm mm-unstable branch. Its filename is mm-mmap-vma_merge-explicitly-assign-res-vma-extend-invariants.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-vma_merge-explicitly-assign-res-vma-extend-invariants.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Lorenzo Stoakes Subject: mm/mmap/vma_merge: explicitly assign res, vma, extend invariants Date: Wed, 22 Mar 2023 20:18:59 +0000 Previously, vma was an uninitialised variable which was only definitely assigned as a result of the logic covering all possible input cases - for it to have remained uninitialised, prev would have to be NULL, and next would _have_ to be mergeable. The value of res defaults to NULL, so we can neatly eliminate the assignment to res and vma in the if (prev) block and ensure that both res and vma are both explicitly assigned, by just setting both to prev. In addition we add an explanation as to under what circumstances both might change, and since we absolutely do rely on addr == curr->vm_start should curr exist, assert that this is the case. Link: https://lkml.kernel.org/r/83938bed24422cbe5954bbf491341674becfe567.1679516210.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Reviewed-by: Liam R. Howlett Cc: David Hildenbrand Cc: Matthew Wilcox (Oracle) Cc: Vernon Yang Signed-off-by: Andrew Morton --- --- a/mm/mmap.c~mm-mmap-vma_merge-explicitly-assign-res-vma-extend-invariants +++ a/mm/mmap.c @@ -911,7 +911,7 @@ struct vm_area_struct *vma_merge(struct { pgoff_t pglen = (end - addr) >> PAGE_SHIFT; pgoff_t vma_pgoff; - struct vm_area_struct *curr, *next, *res = NULL; + struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; int err = -1; bool merge_prev = false; @@ -939,14 +939,18 @@ struct vm_area_struct *vma_merge(struct else next = NULL; /* case 5 */ - /* verify some invariant that must be enforced by the caller */ + /* + * By default, we return prev. Cases 3, 4, 8 will instead return next + * and cases 3, 8 will also update vma to point at next. + */ + res = vma = prev; + + /* Verify some invariant that must be enforced by the caller. */ VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(curr && end > curr->vm_end); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); VM_WARN_ON(addr >= end); if (prev) { - res = prev; - vma = prev; vma_start = prev->vm_start; vma_pgoff = prev->vm_pgoff; /* Can we merge the predecessor? */ @@ -957,6 +961,7 @@ struct vm_area_struct *vma_merge(struct vma_prev(vmi); } } + /* Can we merge the successor? */ if (next && mpol_equal(policy, vma_policy(next)) && can_vma_merge_before(next, vm_flags, @@ -997,6 +1002,10 @@ struct vm_area_struct *vma_merge(struct adj_start = -(prev->vm_end - addr); err = dup_anon_vma(next, prev); } else { + /* + * Note that cases 3 and 8 are the ONLY ones where prev + * is permitted to be (but is not necessarily) NULL. + */ vma = next; /* case 3 */ vma_start = addr; vma_end = next->vm_end; _ Patches currently in -mm which might be from lstoakes@gmail.com are mm-prefer-xxx_page-alloc-free-functions-for-order-0-pages.patch mm-refactor-do_fault_around.patch mm-pefer-fault_around_pages-to-fault_around_bytes.patch maintainers-add-myself-as-vmalloc-reviewer.patch mm-remove-unused-vmf_insert_mixed_prot.patch mm-remove-vmf_insert_pfn_xxx_prot-for-huge-page-table-entries.patch drm-ttm-remove-comment-referencing-now-removed-vmf_insert_mixed_prot.patch fs-proc-kcore-avoid-bounce-buffer-for-ktext-data.patch fs-proc-kcore-convert-read_kcore-to-read_kcore_iter.patch iov_iter-add-copy_page_to_iter_atomic.patch mm-vmalloc-convert-vread-to-vread_iter.patch mm-mmap-vma_merge-further-improve-prev-next-vma-naming.patch mm-mmap-vma_merge-fold-curr-next-assignment-logic.patch mm-mmap-vma_merge-explicitly-assign-res-vma-extend-invariants.patch mm-mmap-vma_merge-init-cleanup-be-explicit-about-the-non-mergeable-case.patch